Today, I located and drilled the rivet holes to attach the HS ribs to the rear spar. This is where one really starts wishing for one of Van's newer matched-hole kits. I spent a lot of time, staring at the plans, measuring, clamping and unclamping to get the posititions of the ribs just right. I used the aluminum strips I made before to locate the ribs on the spar by simulating the placement of the skins. This seems to work quite well.
The only snag was a rivet hole that came out a little too closer than the standard spec to the edge of one of the ribs. This happened because I drilled the holes in the spar along with all of the others. I shuold have waited until today to drill those holes. Given all of the reinforcement around this rivet I doubt it could ever pull loose. I sent a support request to Van's to get their opinion.
